Work hardening analysis in a lean duplex stainless Steel 2304 after low deformation by cold rolling

Abstract

The deformation mechanism of lean duplex stainless steel (LDSS) is overly complex not only by their dual phase microstructure, but also due to metastable austenite, which can deform by different mechanisms and transform to martensite by strain. The purpose of this study was to investigate the mechanisms of deformation by tensile test on low deformed cold-rolled samples (4%-22%) of a 2304 LDSS. The microstructure was analyzed by X-ray diffraction, optical microscopy, electron backscattered diffraction and transmission electron microscopy. It was observed the formation of mechanical twinning, ε-martensite, and α’-martensite which evidenced the TRIP effect. The strain hardening rate was calculated and analyzed by Holomon and Crussard-Jaoul modeling together with instantaneous strain hardening exponent, and three operating mechanisms were observed: twinning, dislocations slipping, and strain induced martensite formation (SIM). Brass texture had compromised SIM transformation. The fractography analysis of tensile specimens showed quasi-cleavage occurrence, and dimples formation for this range of pre-deformation.